The polyphenylene ether resins are characterized by a unique combination of chemical, physical and electrical properties over a temperature range of more than 650.degree. F., extending from a brittle point of about -275.degree. F. to a heat distortion temperature of about 375.degree. F. This combination of properties renders the polyphenylene ethers suitable for a broad range of applications. However, in spite of the aforementioned beneficial properties, the usefulness of the polyphenylene ether resins is limited in some applications as a consequence of processability, impact resistance and chemical resistance.
Finholt (U.S. Pat. No. 3,379,792) discloses polymer blends wherein the processability of polyphenylene ether resins may be improved by blending with from 0.1 to 25% by weight of a polyamide. However, the advantages of the Finholt invention are limited by the fact that when the concentration of the polyamide exceeds 20% by weight, appreciable losses in other physical properties result. Specifically, there is no, or at best poor, compatibility between the polyphenylene ether and the polyamide such that phase separation of the resins occurs on molding or the molded article is inferior in mechanical properties.
Ueno et al. (U.S. Pat. No. 4,315,086) discloses polyphenylene ether blends having improved chemical resistance without a loss of other mechanical properties by blending therewith a polyamide and a specific compound selected from the group consisting essentially of A) liquid diene polymers, B) epoxy compounds and C) compounds having in the molecule both of i) an ethylenic carbon-carbon double bond or carbon-carbon triple bond and ii) a carboxylic acid, acid anhydride, acid amide, imide, carboxylic acid ester, amino or hydroxy group.
Finally, Kasahara et al (EP46040) discloses the use of a copolymer comprising units of a vinyl aromatic compound and either an alpha, beta-unsaturated dicarboxylic acid anhydride or an imide compound thereof as a modifier to an impact resistant polyphenylene ether-polyamide blend for improved heat resistance and oil resistance.
The present applicants have disclosed novel polyphenylene ether-polyamide blends having improved impact strength, elongation, chemical resistance, processability and/or heat resistance as well as reduced water absorption as compared to unmodified polyphenylene ether-polyamide compositions.
Specifically, applicants have discovered novel resin compositions having the aforementioned properties comprising a blend of a polyamide with or without a conventional polyphenylene ether and a property improving amount of the effective functionalized-polyphenylene ether compatibilizer described in detail below.
The functionalized-polyphenylene ether is a polyphenylene ether polymer which has been reacted with another compound which contains in its molecule both of two groups (i) and (ii) which are described in detail below. The molecule containing both groups (i) and (ii) is nominally an "acyl-functional"moiety within the broad definition of such materials below. The group (ii) portion of the molecule is considered to be a polyamide-philic moeity.
Accordingly, the functionalized-polyphenylene ether compatibilizing compound is provided by the reaction of a polyphenylene ether polymer and a compound containing the requisite, aforementioned groups (i) and (ii). The resultant product is the reaction residue of the polyphenylene ether polymer and the group (i), (ii) molecule.
An example of a molecule containing the requisite group (i) and group (ii) moieties is trimellitic anhydride acid chloride.
It has been discovered, for example, that polyphenylene ether polymer may be reacted with trimellitic anhydride acid chloride (TAAC) and the reaction product (PPE-TAAC) functions very effectively as a compatibilizer for polyphenylene ether-polyamide blends. With proper impact modification, the resultant blends exhibit very attractive physical properties such as high heat distortion temperature (HDT), good impact strength and mechanical properties, low shrinkage, and outstanding chemical resistance and hydrolytic stability for many end-use applications.
It also has been discovered that PPE-TAAC is superior to maleic anhydride as a compatibilizer for polyphenylene ether/polyamide (PPE/PA) blends in many respects.
For example, PPE-TAAC compatibilizer offers better color stability. Significant discoloration after extrusion was observed for PPE/Nylon (6/6) blends which were compatibilized with maleic anhydride in the manner taught by UENO, et al. Such discoloration was not evident in PPE/PPE-TAAC/Nylon 6/6 blends of the present invention.
The functionalized-polyphenylene ether compatibilizer also offers improved dimensional stability. Higher mold shrinkage was observed in prior art PPE/Nylon (6/6)/maleic anhydride blends in comparison with PPE/PPE-TAAC/Nylon (6/6) blends of the present invention having comparable physical properties.
The functionalized-polyphenylene ether compatibilizer also offers higher matrix ductility. Impact modified PPE/Nylon (6/6)/maleic anhydride blends from the prior art exhibited significantly lower Izod impact strength and less ductile failure behavior in a falling dart test than corresponding PPE/PPE-TAAC/Nylon (6/6) blends of the present invention. The mode of ductile failure can be an extremely important consideration when choosing a thermoplastic for various end-use applications.
The functionalized-polyphenylene ether compatibilizer provides better phase dispersion and interfacial adhesion. PPE/Nylon (6/6)/maleic anhydride blends were judged from morphology and solubility test results to have much inferior phase dispersion and interfacial adhesion compared to PPE/PPE-TAAC/Nylon (6/6) blends of the present invention.